Lymphoid and tumorcell lines have been established in vitro from the same patient including those with malignant melanoma and colon carcinoma. Tumor cell lines from patients with carcinoma of the gall bladder were also established. Cell products monitored included melanin, immunoglobulin, carcinoembryonic antigen, glucose-6-phosphate dehydrogenase isoenzymes and hormones. Characterization of all the cell lines included cytogenetic analysis, growth in immunosuppressed mice, cytotoxicity assays, estrogen and progesterone receptor proteins, mycoplasma contamination, morphology including ultramorphology, growth patterns, and media requirements. The cell lines are maintained in cultured, preserved in a cell bank, and made available to other investigations. New techniques for establishing human T lymphoid cell lines from normal individuals and patients with malignancy were applied. A survey of the presence of double minute (dm) chromosomes in the cell lines was carried out. The significance of dm in tumor cells is currently under investigation.